It is thought that Y chromosome is crucial for the normal function of the immune system and without it the body struggles to eliminate cancerous cells, and amyloid plaques in the brain which cause Alzheimer’s disease.

Now scientists at Uppsala University in Sweden have found it is possible to test for loss of the chromosome in a breakthrough which could lead to widespread screening which could pick up which men are at risk so that early health interventions could be made.

"The addition of testing in the general population could give medical practitioners the possibility of using preventive strategies in men at risk,” said lead author Prof Lars Forsberg of Uppsala University.

If we could predict which men have an increased risk, we could watch them closely for the development of disease and also use appropriate preventive treatments.Prof Lars Forsberg

"For example, in cancer, primary tumours are usually not deadly; it is the metastatic process that it normally responsible for deaths.

"If we could predict which men have an increased risk, we could watch them closely for the development of disease and also use appropriate preventive treatments.

“In short, the widespread use of testing could radically decrease male mortality rates, and even perhaps eliminate the difference in life expectancy between the sexes."

In humans each cell contains 23 pairs of chromosomes, 22 of which look the same and are called autosomes, and a 23rd pair which are the sex chromosomes. Women have two copies of the X chromosome, while males have one X and one Y chromosome.

It has been suggested that women live longer because they do not have a Y chromosome to lose. The average man in Britain lives until 79.5 while women can expect to live to 83.2.

The loss of the Y chromosome - known as LOY- is known to affect up to 20 per cent of men who are aged over 80, and is the most common genetic mutation acquired during a man's lifetime.

The team studied more than 3,200 men with an average age of 73 and found 17 per cent of them showed LOY in blood cells, which increased with age.

Those with an existing diagnosis of Alzheimer's disease (AD) had a higher degree of LOY, and LOY was also a marker for the likelihood of developing the disease during the follow-up period.

“Our working hypothesis is that the normal function of the immune system in particular the ability to recognize and eliminate the abnormal cells, i.e. cancer cells and cells in the brain forming amyloid plaques, is compromised in subjects showing high degree of loss of Y,” added Prof Forsberg.

The team is now investigating the functional effects of LOY, and looking at its role in different groups of men and in other diseases, to understand better which types of cancer are associated with LOY, as well as whether there is a link with early signs of dementia, for example mild cognitive impairment.

The findings were published in the American Journal of Human Genetics.